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\multicolumn{2}{|c|}{\LARGE\bf THE\hspace*{1cm}STAR\hspace*{1cm}FORMATION\hspace*{1cm}NEWSLETTER} \\ [0.3cm]
\multicolumn{2}{|c|}{\large\em An electronic publication dedicated to early stellar evolution and molecular clouds} \\ [0.3cm]
{\hspace*{0.8cm} No. 13 --- 3 Sept 1993 } & \multicolumn{1}{r|}{Editor: Bo Reipurth (reipurth@eso.org)\hspace*{0.8cm}} \\ [-0.1cm]
& \\ \hline
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\vspace*{1cm}
\begin{center}
{\Large\em Abstracts of recently accepted papers}
\end{center}
\vspace*{0.6cm}
%% Between these brackets you write the title of your paper:
{\large\bf{From T Tauri Stars to Protostars: Circumstellar Material and
Young Stellar Objects in the $\rho$ Ophiuchi Cloud }}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Philippe Andr\'e and Thierry Montmerle }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Service d'Astrophysique, Centre d'Etudes de Saclay,
F-91191 Gif-sur-Yvette Cedex, France }
%% Within the following brackets you place your text:
{ We present the results of a 1.3-mm continuum survey for cold
circumstellar dust, conducted with the IRAM 30-m telescope on a sample
of over a hundred young stellar objects (YSOs) in or near the
$\rho$ Ophiuchi molecular cloud.
To correlate the millimeter results with other source properties, we have
used the IR classification of Wilking, Lada, \& Young, but revising it
critically to take into account factors such as heavy extinction.
We find a sharp threshold in millimeter flux density at an infrared
spectral index $\alpha_{IR}(2.2-10 \mu$m)~$\simeq -1.5$, which
is also visible in the IRAM 30-m survey of Taurus-Auriga T Tauri stars by
Beckwith et al. We show that this threshold is well correlated with a disk
opacity transition at $\lambda \simeq 10\ \mu$m, and can be used to set
a physical boundary between Class~III and Class~II IR sources.
At a detection sensitivity of $\sim$~20--30~mJy/beam ($3\sigma $) at 1.3~mm,
less than 15~\% of the Class~III IR sources, but
as much as 60~\% of the Class~II sources and 70--90~\% of the
Class~I sources, are detected. Statistical studies show that
the peak 1.3-mm fluxes of deeply embedded Class~I sources, currently referred
to as ``protostars'', and of ``classical'' T Tauri
stars (Class~II sources), are comparable within a factor of 2
at the angular resolution of the telescope (12" FWHM, or a linear
diameter $\sim$ 2,000 AU).
Maps of the millimeter emission are consistent
with the presence of unresolved disks
%on the order of 100~AU in radius
around Class~II sources
and of resolved, extended envelopes
%a few $10^3$~AU in radius
around Class~I sources. Therefore, the difference between Class~I and
Class~II YSOs lies mainly in the {\it spatial distribution} of
their circumstellar dust. Converting the integrated millimeter fluxes
derived from our maps into masses, we
find that: ($i$) $\sim 30$~\% of the Class~II sources have masses larger than
the ``minimum mass solar nebula'' ($\sim 0.01\ M_\odot$); ($ii$) the
envelopes of Class~I sources contain
more circumstellar material than Class~II disks, consistent with Class~I
sources being younger than Class~II sources, but ($iii$) their total
circumstellar masses are not large ($\leq 0.1\ M_\odot$). This suggests
that the central object has already accumulated most of its final
stellar mass at the Class~I stage. By contrast, a very strong 1.3~mm
emission is found toward two deeply embedded outflow sources (IRAS~16293
and VLA~1623) which remain undetected shortward of 25 $\mu$m. These
latter sources belong to a new class of YSOs (``Class 0'') introduced by
Andr\'e, Ward-Thompson, \& Barsony, which are surrounded by
significantly
larger amounts of circumstellar material ($\sim 0.5\ M_\odot $ or more),
still to be accreted by the central protostellar core.
Class~0 YSOs appear to be significantly younger, and
therefore at an earlier protostar stage, than Class~I sources. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{ The HH83 Molecular Cloud: Gone With The Wind }}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ John~Bally$^1$, Alain~Castets$^2$ \ and Gilles~Duvert$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ { Department of Astrophysical, Planetary, and Atmospheric Sciences
and
Center for Astrophysics and Space Astronomy
Campus Box 389, University of Colorado, Boulder, CO 80309, USA }
~~~bally@janos.colorado.edu \\
$^2$ { Laboratoire d'Astrophysique, Observatoire de Grenoble,
BP 53X, F- 38041 Grenoble CEDEX, France \\
castets@gag.observ-gr.fr
}
%% Within the following brackets you place your text:
{
The HH83 optical outflow and its host cloud core has been
mapped in the J=1-0 and J=2-1 transitions of CO and its isotopes.
The $^{12}$CO
and $^{13}$CO maps exhibit a hot spot, a column density enhancement, and
increased velocity dispersion at the position of the young star
driving the optical jet. The cloud exhibits an overall
velocity gradient along its major
axis, which if interpreted as rotation would be consistent with
a rotation axis roughly aligned with the optical jet.
The $^{13}$CO linewidth and a region of enhanced velocity gradients
surrounding HH83 IR are used to constrain the mass of this
star and surrounding gas.
In addition to the compact core, several other sub-condensations
in the HH83 cloud have been identified in $^{13}$CO map. The cloud
may contain a pair of cavities
symmetrically located on either side of HH83 IR that lie roughly
along the axis defined by the optical jet.
A very low velocity and poorly collimated molecular outflow
with a large redshifted lobe and a small blueshifted one
is associated with HH83. This molecular outflow
has one of the lowest terminal
velocities of any known source (about 5 km~s$^{-1}$), a small total mass
(0.1 to 0.2 M$_{\odot}$), and is one of the least energetic molecular flows
($2 \times 10^{43}$ ergs) known.
In this system, the Herbig-Haro jet is the most energetic component
and dominates the energy and momentum of the CO emitting lobes.
The outflow from HH83 IR has ``blown out'' of the HH83 molecular
cloud and may be interacting with predominantly
atomic gas in the intercloud medium. The morphology and kinematics
of the HH83 outflow suggests that it may be in a
late stage of evolution.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{The Arcetri Catalogue of H$_2$O Maser Sources Update}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
%%{\bf{ First Author$^1$, Second Author$^2$ \ and Third Author$^3$ }}
{\bf{ J. Brand$^{1,2}$, R. Cesaroni$^1$, P.Caselli$^3$, M. Catarzi$^4$,
C. Codella$^{2,5}$, G. Comoretto$^1$, G.P. Curioni$^1$, P. Curioni$^1$,
S. Di Franco$^5$, M. Felli$^1$, C. Giovanardi$^4$, L. Olmi$^5$, F. Palagi$^4$,
F. Palla$^1$, D. Panella$^1$, G. Pareschi$^3$, E. Rossi$^1$, N. Speroni$^4$,
G. Tofani$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Osservatorio Astrofisico di Arcetri, Florence, Italy} \\
$^2$ {Istituto di Radioastronomia C.N.R., Via Irnerio 46, I-40126 Bologna,
Italy} \\
$^3$ {Dipartimento di Astronomia, Univ. di Bologna, Italy} \\
$^4$ {C.N.R., Gruppo Naz. Astronomia, U.d.R., Arcetri, Florence, Italy} \\
$^5$ {Dipartimento di Astronomia e Scienza dello Spazio, Florence, Italy}
%% Within the following brackets you place your text:
{An update is presented of the Arcetri Atlas of water masers (Comoretto et al.,
1990). It contains the results of observations of water masers with the
Medicina 32-m antenna. The observed sources were all discovered in the period
1989-1993, and were found either directly in the course of our own programs
or were taken from the literature in which case they were re-observed
at Medicina. We give the observed parameters of 213 sources in tabular form,
and present {\it all} the spectra of the 141 detections.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. Astroph. Suppl.}
\vspace*{0.5cm}
{\large\bf{First Results of the CIDA Schmidt Survey:
Selected Zones in Taurus-Auriga}}
%
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
%
{\bf {Cesar Brice{\~{n}}o$^1$, Nuria Calvet$^1,2$, Mercedes Gomez$^3$, Lee W. Hartmann$^3$, Scott J. Kenyon$^3$, and Barbara A. Whitney$^3$}}
%
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
%
$^1$ {Centro de Investigaciones de Astronom{\'\i}a,
Ap. P. 264, M{\'e}rida 5101-A, Venezuela} \\
{E-mail: emsca!cida!briceno@conicit.ve, ncalvet@conicit.ve} \\
%
$^2$ {Grup d'Astrofisica de la Societat Catalana de Fisica,
Institut d'Estudis Catalans, Spain} \\
%
$^3$ {Harvard-Smithsonian Center for Astrophysics,
60 Garden St., Cambridge, MA 02138, USA} \\
{E-mail: gomez@cfa.harvard.edu, hartmann@cfa.harvard.edu,
kenyon@cfa.harvard.edu, bwhitney@cfa.harvard.edu}
%
%% Within the following brackets you place your text:
%
{We have begun an objective-prism H$\alpha$ survey of star-forming regions
using the CIDA 1 m Schmidt Camera,
with a limiting magnitude $ V \approx 18$. We report here first
results for selected areas of the Taurus-Auriga molecular clouds. Of the list of
candidates found in the objective-prism plates, 12 stars have
been confirmed as pre-main sequence by the detection of the Li I 6707 $\AA$
absorption line. Five of these stars are in the dark cloud L1544,
where only one T Tauri star was previously known. The new stars have
very late spectral types and most have estimated masses between 0.2
M$_{\odot}$ and 0.3 M$_{\odot}$.}
%
% Here you write which journal accepted your paper, for example:
%
{ Accepted by PASP }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{Stellar Density Enhancements Associated with IRAS Sources in
L1641}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Hua Chen$^1$, Alan T. Tokunaga$^2$ \ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138, USA} \\
$^2$ {Institute for Astronomy, 2680 Woodlawn Dr. Honolulu, HI 96822, USA }
%% Within the following brackets you place your text:
{We obtained H and K' images of 59 IRAS sources associated with
dense molecular gas in L1641. Some of the sources were also imaged
in narrow-band L and M. Using these near-IR images and
photometry, we are able to identify the near-IR counterparts for most of
the IRAS sources. The spectral energy distributions of the sources
suggest that all of them are young stellar objects (Class I and II
sources). Most importantly, we find in this study that 14 IRAS sources
are associated with small (but statistically significant) groupings of
bright near-IR sources defined as stellar density enhancements
(SDEs). The spatial distribution of young stars in the Orion A
molecular cloud can be characterized by a range of stellar densities,
from the Trapezium Cluster, to the SDEs, to individual stars. We conjecture
that the SDEs are regions of continuous star formation within or around
dense molecular cores and that they may represent an important mode of star
formation in L1641. If true, adjustments to the standard star formation
model may be required.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. Supplement Series}
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{On the Theory of Astronomical Masers in Three Dimensions}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Moshe Elitzur }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Department of Physics and Astronomy, University of Kentucky,
Lexington, KY 40506, USA}
%% Within the following brackets you place your text:
{In the standard theory of three dimensional astronomical masers, the
radiation field is described as if the source were comprised of a collection
of linear masers, an approximation that has been justified by the highly
beamed nature of the radiation. Recently, Neufeld has noted potential
difficulties with this description and has supplied the general expressions
for the maser problem without assuming beaming at the outset. The
consequences of these general expressions, which have been formulated already
in 1974 by Bettwieser and Kegel, are analyzed here. To leading order, the
standard theory is shown to provide the correct description of three
dimensional masers and its results remain intact, but only within a frequency
core whose half-width is $x_s\Delta\nu_D$, where $\Delta\nu_D$ is the Doppler
width and $x_s$ is a dimensionless parameter. For any given geometry, $x_s$
is $\sim 1/\theta_{sat}$, where $\theta_{sat}$ is the beaming angle of a maser
with that geometry that has just saturated. For typical pumping schemes,
$x_s$ is $\sim$ 2 in spherical masers, $\sim$ 2.5--3 in disk masers and $\sim$
3--5 in cylindrical masers. For frequencies outside this core region, maser
operation corresponds to a mode that will be called {\it suppressed} and the
standard theory breaks down. In this frequency domain, interaction with core
rays that are slightly slanted to the direction of propagation suppresses
photon production. In contrast with the core region, in the suppressed regime
the rate of maser photon generation never reaches the maximum allowed by the
pump processes; this regime effectively corresponds to a maser whose inherent
strength is weaker than that of a linear maser whose properties are otherwise
identical. Observed maser radiation is effectively confined to the core
region since frequencies in the suppressed domain are practically
unobservable. In essence, $x_s$ provides an effective cutoff, defining a
width at zero intensity that depends on the geometry but is unaffected by
growth at line center. In practice, suppression only affects extreme maser
outbursts. Their profiles change in such a way that when fitted with a
Gaussian, the linewidth decreases when the line center intensity increases,
even for masers that are saturated at the line core --- in marked contrast
with the predictions of standard analysis of maser linewidths. This behavior
could perhaps be related to the inverse relationship between intensity and
linewidth displayed in some intense H$_2$O maser flares in star forming
regions. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{The Multiplicity of T Tauri Stars in the Star Forming Regions
Taurus-Auriga and Ophiuchus-Scorpius: A 2.2 $\mu$m Speckle Imaging Survey
}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ A. M. Ghez$^1$, G. Neugebauer$^2$ \ and K. Matthews$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Steward Observatory, University of Arizona, Tucson, AZ 85721, USA} \\
$^2$ {California Institute of Technology 320-47, Pasadena, CA 91125, USA}
%% Within the following brackets you place your text:
{
We present the results of a magnitude limited (K $\leq$ 8.5 mag) speckle imaging
survey of 69 T Tauri stars in the star forming regions Taurus-Auriga
and Ophiuchus-Scorpius. Thirty-three companion stars were found with
separations ranging from 0.$''$07 to 2.$''$5; 9 are new detections.
This survey reveals a distinction
between the classical T Tauri stars (CTTS) and the weak-lined T Tauri stars
(WTTS) based on the binary star frequency as a function of separation: {\it the
WTTS binary star distribution is enhanced at the closer separations
($\leq$50 AU) relative to the CTTS binary star distribution.} We suggest that
the nearby companion stars shorten the accretion time scale in multiple star
systems, thereby accounting for the presence of WTTS that are coeval with many
CTTS.
The binary star frequency in the projected linear
separation range 16 to 252 AU for T Tauri stars (60[$\pm$17]\%) is a
factor of 4 greater than that of the solar-type main sequence stars
(16[$\pm$3]\%). Given the limited separation range of this survey, the rate at
which binaries are detected suggests that {\it most, if not all, T Tauri stars
have companions.} We propose that the observed overabundance of
companions to T Tauri stars is an evolutionary effect, in which triple and
higher order T Tauri stars are disrupted by close encounters with
another star or system of stars.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. J. }
\vspace*{0.5cm}
\large
{\bf A 1.3 mm survey for circumstellar dust around
young Chamaeleon objects}\\[0.2cm]
\normalsize
{\bf Th. Henning$^1$, W. Pfau$^2$, H. Zinnecker$^3$, and T. Prusti$^4$}\\[0.2cm]
$^1$ Max-Planck-Gesellschaft, AG ``Staub in Sternentstehungsgebieten'',
Schillerg\"a\ss chen 2-3, 07745 Jena, Germany\\
$^2$ Universit\"ats-Sternwarte, Schillerg\"a\ss chen 2, 07740 Jena, Germany\\
$^3$ Institut f\"ur Astronomie und Astrophysik, Am Hubland, 97074 W\"urzburg,
Germany\\
$^4$ Space Science Department, ESTEC, Postbus 299, 2200 AG Noordwijk, The
Netherlands\\[0.2cm]
We present the results of the first 1.3 mm continuum survey of young stellar
objects in the Chamaeleon I and II dark clouds. 36 objects were observed,
including five intermediate-mass stars. We detected emission from about 50\%
of the sources. At 1.3 mm, none of the sources with a spectral index
{\it a}(2.2-25 $\mu$m) smaller than -1 could be found. There is no
correlation between 1.3 mm flux and H$\alpha$ equivalent width.
The detected millimetre radiation is most probably thermal emission from
cold circumstellar dust grains.\\
We combined the measured millimetre fluxes with infrared observations and
modelled the broad-band energy distributions by both an exact
spherically-symmetric radiative transfer model including scattering and
properties of different dust populations and a model for geometrically
thin disks with parametrized temperature and density distribution.
In this way, we were able to constrain the parameters of the emission
regions.\\[0.2cm]
Accepted by Astronomy and Astrophysics
\vspace*{0.5cm}
{\large\bf{ `Cored Apple' Bipolarity : A Global Instability to Convection in Radial Accretion? }}
{\bf{ R.N. Henriksen$^1$ and D. Valls--Gabaud$^{1,2}$ }}
$^1${Astronomy Group, Stirling Hall, Queen's University,
Kingston, Ontario K7L 3N6, Canada}\\
$^2${Institut d'Astrophysique de Paris, 98 bis, Bld. Arago, 75014 Paris,
France }
{We propose that the prevalence of bipolarity in Young Stellar Objects (
YSO's) is due
to the fine tuning
that is
required for spherical accretion of an ambient medium onto a
central node. It is shown that there are two
steady modes
that are more likely than radial accretion,
each of which is associated with a hyperbolic central point
in the
meridional stream lines, and consequently with either an equatorial inflow
and an axial ejection or {\it vice versa}. In each case the stream lines pass
through a thick accretion torus, which is better thought of as a
standing pressure wave rather than as a relatively inert Keplerian
structure. We base our arguments on a simple
analytic example, which is topologically generic, wherein each bipolar
mode is created by the `rebound' of accreting matter under the action of
the
thermal, magnetic, turbulent and centrifugal
pressures created in the flow. In both bipolar modes the
presence of non-zero angular momentum implies axial
regions wherein the pressure is first reduced below the value at infinity
and then becomes negative, where the solution fails because rotating material
can not enter this region without `suction'. The models
thus have empty `stems' where the activity of the central source must
dominate. So the basic engine of the bipolar flow discussed here is
simply the rebound of freely falling material from a thick
pressure disc into an axial low pressure region. The low mass, high
velocity outflow must be produced in this region by an additional
mechanism. This is reminiscent of the `cored apple' structure observed
recently in the very young bipolar source VLA 1623.
}
{ Accepted by M.N.R.A.S. Preprints available from {\tt dgabaud@lola.phy.queensu.ca} }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{An Observational Estimate of the Probability of Encounters \\
Between Mass-Losing Evolved Stars and Molecular Clouds}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Joel H. Kastner$^1$ \ and P.C. Myers$^2$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {MIT Haystack Observatory, Rt.\ 40, Westford, MA 01886, USA} \\
$^2$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
MS 42, Cambridge, MA 02138, USA}
%% Within the following brackets you place your text:
{One hypothesis for the elevated abundance of $^{26}$Al present during the
formation of the solar system is that an asymptotic giant branch (AGB) star
expired within the molecular cloud (MC) containing the protosolar nebula.
To test this hypothesis for star forming clouds at the present epoch, we
compared nearly complete lists of rapidly mass-losing AGB stars and MCs in
the solar neighborhood and identified those stars which are most likely to
encounter a nearby cloud. Roughly ten stars satisfy our selection criteria.
We estimated probabilities of encounter for these stars from the position of
each star relative to cloud CO emission and the likely star-cloud distance
along the line of sight. Typical encounter probabilities are $\sim1$\%. The
number of potential encounters and the probability for each star-cloud pair
to result in an encounter suggest that within 1 kpc of the Sun, there is a
$\sim$1\% chance that a given cloud will be visited by a mass-losing AGB
star over the next million years. This estimate is dominated by the
possibility of encounters involving the stars IRC+60041 and S Cep. Over a
MC lifetime, the probability for AGB encounter may be as high as $\sim$70\%.
We discuss the implications of these results for theories of $^{26}$Al
enrichment of processed and unprocessed meteoritic inclusions. If the
$^{26}$Al in either type of inclusion arose from AGB-MC interaction, the low
probability estimated here seems to require that AGB-MC encounters trigger
multiple star formation and/or that the production rate of AGB stars was
higher during the epoch of solar system formation than at present. Various
lines of evidence suggest only the more massive ($5-8 M_\odot$) AGB stars
can produce significant $^{26}$Al enrichment of star-forming clouds.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Ap. J. }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{A Rotating Gaseous Disk Around the T Tauri Star
GM Aurigae}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ D. W. Koerner$^1$, A. I. Sargent$^2$ \ and S. V. W. Beckwith$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Div. of Geological and Planetary Sciences, 170-25 Caltech,
Pasadena, CA 91125, USA} \\
$^2$ {Div. of Physics, Mathematics, and Astronomy, 105-24 Caltech,
Pasadena, CA 91125, USA} \\
$^3$ {Max-Planck-Institut f\"ur Astronomie, K\"onigstuhl, D-900
Heidelberg 1, Germany}
%% Within the following brackets you place your text:
{We report the detection of a gaseous circumstellar disk around
a relatively old T Tauri star, GM Aurigae.
Maps at $4''$ resolution in $\lambda$ = 1.4 mm continuum emission and
in the $^{13}CO$ (2--1) line reveal unresolved and compact dust and
gas associated with the stellar position and at the core of a
larger rotating gaseous disk, 950 $\times$ 530 AU in extent.
The mean velocity
gradient across the disk, which is oriented along PA $\sim$ 50$^\circ$,
is consistent with rotation about an axis at PA=140$^\circ$.
The structure observed in $^{13}CO$ aperture synthesis maps
agrees well with synthetic maps of the gas emission,
generated from a model. For a disk that is inclined 30$^\circ$ from
face on in Keplerian rotation, we derive a 0.80-$M_{\odot}$ central mass
(star $+$ disk), a systemic velocity, $v_{\rm hel}$, of 15.38 km s$^{-1}$,
and a mass, 0.1 $M_{\odot}$. The spectral energy distribution of the dust
continuum emission suggests a very similar mass, 0.09 $M_{\odot}$.
%This is the abstract of your paper}
% Here you write which journal accepted your paper, for example:
{ Accepted by Icarus }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{A multi-transitional molecular and atomic line study of S140}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Nigel R. Minchin $^1$, Glenn J. White $^1$ and Rachael Padman $^2$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Physics, Queen Mary and Westfield College,
Univ. of London, Mile End Road, London E1 3NS, U.K.} \\
$^2$ {Mullard Radio Astronomy Observatory, Cavendish Laboratory,
Madingley Road, Cambridge CB3 0HE, U.K.}
%% Within the following brackets you place your text:
{We present high-angular resolution maps of the S140 molecular cloud in various
transitions of the $^{12}$CO, $^{13}$CO and C$^{18}$O molecules and
single-channel observations of the $^3$P$_1$$\rightarrow$$^3$P$_0$ line of
neutral atomic carbon (CI). Velocity channel maps of the $^{12}$CO lines show a
systematic shift of the emission peak away from the outflow source with
increasing velocity offset from the line centre. The blue and redshifted
outflow lobes are separated by $\sim$35 arcsec (0.15 pc) in projection and the
outflow axis is believed to be directed close to the observers' line-of-sight.
The masses of the blue and redshifted outflow lobes were found to be 19.5 and
8.1M$_{\odot}$ respectively, giving a total mass for the outflow of
27.6M$_{\odot}$. The higher J-level $^{12}$CO lines are strongly self-absorbed,
with the amount of self-absorption varying with position across the mapped
region.
All the $^{12}$CO, $^{13}$CO and C$^{18}$O lines show enhanced main beam
brightness temperatures at the molecular cloud/HII region interface. The
$^{13}$CO line intensities imply the excitation temperature increases from
$\sim$65-70K at the position of the outflow source, to $\sim$250K at the
interface region. The CI emission is mainly confined to a clumpy, elongated
ridge-like feature adjacent to the edge of the molecular cloud and is
coincident with a similar feature seen in $^{12}$CO line emission. The
coincidence of these features contradicts homogeneous cloud models and is
interpreted as evidence that the molecular material is composed of dense clumps
interspersed with a more tenuous interclump medium. A second region of intense
CI emission is located inside a ring of CS emission, implying that $^{12}$CO
here is dissociated by the radiation field from the embedded infrared cluster
and {\em not} the external radiation field. Observed positions on the PDR
have significantly higher values of $T_{\rm {mb}}$(CI)/$T_{\rm
{mb}}$($^{13}$CO) than for the general cloud, implying $N({\rm
CI})$/$N(^{13}{\rm CO})$ is likely to be significantly higher for positions on
the PDR than in the general molecular cloud. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. Astrophys. }
\vspace*{0.3cm}
{\large\bf{Dust coagulation in dense molecular clouds - The formation of
fluffy aggregates}}
{\bf{V.~Ossenkopf}}
{ Max-Planck-Gesellschaft,
Schillerg\"a\ss chen\,2, 07745 Jena, Federal Republic of Germany}
{Dust extinction observations and the calculation of gas-dust dynamics
indicate that in dense clumps of molecular clouds dust grains coagulate
efficiently.
We set up a detailed model for the dust coagulation process in dense
cores of molecular clouds without beginning star formation. We took
into account the effects of thermal,
turbulent, gravitational motion, motion from incidential particle
asymmetries, grain rotation, charges, and the accretion of molecules onto
the particles. For most effects, we developed new formalisms. For the first time, we explicitly considered
the irregularity and changing fluffiness of the clusters produced in the coagulation process.
The basis for this treatment was an independent numerical simulation of
the structure of such aggregates. Here, we considered especially the
behaviour of aggregates smaller than the fractal limit and composed of
subgrains with a spectrum of sizes. We fitted the structure parameters
by analytic functions which were used in the final model for the coagulation of the interstellar particles.
With this model we carried out numerous simulations of the evolution
of dust grain distributions in dense cores. The particles were
characterized by two parameters, the particle mass and a quantity
related to the internal density of the particles. Different gas
densities, clump models, accretion rates, and initial grain size
distributions were investigated.
It was found that the main force driving the aggregation of dust
particles in dense clumps is turbulence at gas densities below 10$^8$
H-atoms per cm$^3$ and Brownian motion at higher densities. The coagulation
velocity is considerably influenced by electric charges
on the grains.
Both dust coagulation and ice accretion lead to a rapid growth of
the smallest particles whereas the upper grain size limit is only slightly
shifted. The resulting size and density distribution will be narrow
on the grain mass scale but broad in the internal density parameters
of the coagulates.
The total opacity of the resulting distributions of fluffy dust agglomerates
was calculated using effective-medium theories combined with a core-mantle
model for the aggregate particles. The far infrared absorptivity
is enhanced by the factor 3 (at 200 mi) in the first steps
of the coagulation process and hardly influenced by the further coagulation.
For gas densities between $10^6$ and $10^9$ cm$^{-3}$ and timescales
below 10$^5$ yrs, the coagulation process
is efficient in changing the optical properties of the dust particles
but not in the production of large heavy particles.}
{Accepted by Astron.Astrophys}
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{Infrared images, 1.3 mm continuum and ammonia line
observations of IRAS 08076-3556}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ P.Persi$^1$, M.Ferrari-Toniolo$^1$, A.R.Marenzi$^1$, G.Anglada$^3,4$ ,
R.Chini$^2$, E.Kr\"ugel$^2$\ and I.Sepulveda$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Istituto Astrofisica Spaziale,CNR,CP67,00044 Frascati,Italy} \\
$^2$ {Max-Planck Institut fur Radioastronomie,Auf dem Hugel 69
D-53 Bonn,Germany} \\
$^3$ { Department d'Astronomia i Meteorologia, Universitat de Barcelona,
Av.Diagonal 647,08028,Barcelona,Spain} \\
$^4$ {Laboratori d'Astrofisica, Societat Catalana de Fisica,IEC, Spain}
%% Within the following brackets you place your text:
{We present J,H,K,and L' broad--band images, 1.3 mm continuum photometry
and ammonia line observations of IRAS 08076-3556, the energy source of
the Herbig Haro object HH120. Nebulosity is detected in the J,H and K
bands; K and L' images show clearly the embedded young star coincident
with the IRAS position. The energy distribution of the embedded object
places it among the very young Class I sources. The ratio between the
1.3 mm luminosity and the bolometric luminosity is much higher than
Class I sources, and similar to that of the extremely young "Class 0"
sources. The strong 1.3 mm emission is probably due to a circumstellar
dust disk with T$_d$= 20K and M$_d$= 7 10$^{-2}$ $M_{\odot}$.
The observed infrared nebulosity
is most likely due to scattering of radiation from the HH120 exciting source
by the dust associated with mass outflow escaping through the poles of
this circumstellar disk. Finally, IRAS 08076-3556 appears embedded in a
high density core, detected through our NH$_3$ observations, with a
linear size $\leq$ 0.16 pc and a mass of 8 $M_{\odot}$.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. Astrophys.}
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Numerical Simulations of Protostellar Jets with Nonequilibrium
Cooling. \\
III: Three Dimensional Results}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ James M. Stone$^1$ \ and Michael L. Norman$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy, University of Maryland, College Park,
MD 20742-2421, USA} \\
$^2$ {National Center for Supercomputing Applications, University of
Illinois at Urbana-Champaign \\ 5600 Beckman Institute, D-25,
405 North Mathews Avenue, Urbana, IL 61801, USA}
%% Within the following brackets you place your text:
{In the third of three papers, we present three dimensional
time-dependent numerical simulations of the propagation of protostellar
jets into uniform and plane stratified ambient media using a
nonequilibrium treatment of optically thin radiative cooling.
We find the evolution of the jet beam and cocoon is
similar to the results of previous two dimensional simulations, including
the formation of a thin dense shell at the head of the jet.
However, in three dimensions this shell
undergoes significant nonaxisymmetric fragmentation to form
discrete knots and filaments. Knots shed from the head of the jet propagate
nearly ballistically into the ambient gas, and can be characterized as
``interstellar
bullets". On the other hand, variations in the speed of advance of the
Mach disk can cause knots formed in the cooling shell to become embedded
in the jet beam, leading to ``shocked cloudlets". When the jet
propagates through an ambient medium with a lateral density
gradient, the bow shock propagates more slowly in the direction of the
highest densities as expected, leading to a distorted cocoon. However,
we find the orientation of the bow shock at the tip of the jet is time
variable as the dense shell fragments. Synthetic
H$\alpha$ emission maps and position-velocity diagrams are
presented for direct comparison to observations.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Ap. J. }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Anatomy of a Photodissociation Region: High Angular
Resolution Images of Molecular Emission in the Orion Bar}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Jan A. Tauber$^{1,2}$, A.G.G.M. Tielens$^{3,4}$, Margaret Meixner$^1$,
\ and Paul F. Goldsmith$^{5,6}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ Radio Astronomy Laboratory, University of California, Berkeley, USA \\
$^2$ European Space Agency, Astrophysics Division, ESTEC,
Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands \\
$^3$ NASA/Ames Research Center, MS 245-3 Space Sciences Division,
Moffett Field, CA 94035, USA \\
$^4$ Dpt of Astronomy, University of California, Berkeley,
CA 94720, USA \\
$^5$ Five College Radio Astronomy Observatory and
Department of Physics and Astronomy, University of
Massachusetts, Amherst, MA 01001, USA \\
$^6$ National Astronomy and Ionosphere Center, Dpt. of
Astronomy, Cornell University, Ithaca, NY 14853-6801, USA
%% Within the following brackets you place your text:
{We present observations of the molecular component of the
Orion Bar, a prototypical Photodissociation Region (PDR) illuminated by the
Trapezium cluster. The high angular resolution (6$''$-10$''$) that we
have achieved by combining single dish and interferometric observations
has allowed us to examine in detail the spatial and kinematic
morphology of this region, and to estimate the physical characteristics
of the molecular gas it contains. Our observations indicate that this
PDR can be essentially
described as a homogeneously distributed slab of moderately dense material
($\sim$5$\times$10$^4$ cm$^{-3}$), in which are embedded a small number of dense
($>$10$^6$ cm$^{-3}$) clumps. The latter play little or no role in
determining the thickness and kinetic temperature structure of this PDR.
This observational picture is largely supported by PDR model calculations
for this region, which we describe in detail in this work. We also find our
model predictions of the intensities of a variety of
atomic and molecular lines to be in good general agreement with
a number of previous observations.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{High Resolution Images of Shocked Molecular Clumps in the SNR IC443}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Jan A. Tauber$^{1,2}$, Ronald L. Snell$^{3}$,
Robert L. Dickman$^{3,4}$,
\ and L.M. Ziurys$^5$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ Radio Astronomy Laboratory, University of California, Berkeley,
CA 94720, USA \\
$^2$ Current address: ESA Astrophysics Division, ESTEC, P.O. Box
299, NL-2200 AG Noordwijk, The Netherlands \\
$^3$ Five College Radio Astronomy Observatory and
Department of Physics and Astronomy, University of
Massachusetts, Amherst, MA 01001, USA \\
$^4$ Current address: National Science Foundation, Washington,
DC 20550, USA \\
$^5$ Departments of Chemistry and Astronomy, Arizona State
University, Tempe, AZ 85287, USA
%% Within the following brackets you place your text
{We present high angular resolution interferometric observations
of HCO$^+$ J=1$\rightarrow$0 line emission from two molecular clumps
which are being
shocked by the blast wave from the supernova which formed the remnant IC443.
Our observations show that a range of gas densities exist within these
clumps; this fact may explain the mixture of shock velocities inferred
from other observations. Previous studies have shown evidence that
molecular material is being accelerated by
the blast wave in a systematic fashion around one of the clumps that we study.
We show that this phenomenon also occurs at the small spatial scales that
we observe. In addition,
we present evidence that suggests that the velocity field may
correspond to ablation from or a bow-shock around the denser cores
present within the clumps.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Structure of Dense Cores in M17 SW: I. A Multitransition CS and C$^{34}$S Study}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Y. Wang$^1$, D. T. Jaffe$^1$, N. J. Evans II$^1$, M. Hayashi$^2$, K. Tatematsu$^1$ \& S. Zhou$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {University of Texas at Austin, Austin, TX, USA} \\
$^2$ {University of Tokyo, Tokyo, Japan
} \\
$^3$ {University of Illinois, Urbana, IL, USA
}
%% Within the following brackets you place your text:
{We present results of a multitransition
CS and C$^{34}$S study of the M17 SW molecular cloud core.
Fully sampled maps were obtained in
the CS J=1$\rightarrow$0, 2$\rightarrow$1, and 7$\rightarrow$6 lines and the
C$^{34}$S J=2$\rightarrow$1 line with 18$^{"}-$
36$^{"}$
resolution.
Velocity channel maps reveal the
clumpy emission from the dense gas
on scales of about 0.2 pc (20$^{"}$).
The overall agreement in the cloud morphology
among maps of different CS and C$^{34}$S
transitions suggests that all CS and C$^{34}$S lines
originate in the same dense
gas. Excitation and opacity effects probably cause the
modest differences between the maps.
We carried out a detailed excitation analysis of the multitransition
data. The J=2$\rightarrow$1
and J=7$\rightarrow$6 transitions of CS, analyzed with an
LVG radiative transfer model, produced 250-pixel maps of
the volume density
and the CS column density over an area of about 1.8 pc$\times$2.4 pc.
Peaks in the CS and C$^{34}$S line temperature maps
are maxima in column density, but not in density.
The density map shows a fairly uniform, high density (n$\approx$10$^{5.7}$
$cm^{-3}$) throughout the cloud core.
An independent estimate of the gas densities from analysis of the
C$^{34}$S observations confirms the CS results.
Along with other evidence, these results imply
a clumpy cloud model in which the CS emission arises from structures
smaller than our beam.
We compared the observed CS maps with a specific clumpy cloud model
with 179 clumps decomposed from
the C$^{18}$O J=2$\rightarrow$1 maps
(Stutzki \& G\"usten 1990).
Model channel maps of CS were synthesized based on the
clump parameters listed in Stutzki and G\"usten (1990) and were
compared with the observed maps. The gas densities used in the models
were derived
from the clump column densities (based on the C$^{18}$O J=2$\rightarrow$1
emission)
and sizes. Most of the dominant clumps had densities near 10$^5$
$cm^{-3}$.
The resulting synthesized map does not reproduce the
observed CS J=7$\rightarrow$6 emission along the eastern ridge of the core.
By assuming a constant gas density for all clumps, we were
able to synthesize
CS channel maps which reproduce
the observed cloud morphology and the line intensities
reasonably well. A mean clump density in the models
of about 5$\times$10$^{5}$ $cm^{-3}$ (about five times higher than the density derived from
C$^{18}$O) matches the observed CS line ratios and
a CS/H$_{2}$ abundance ratio of about 4$\times$10$^{-9}$ fits the
observed line intensities of the J=1$\rightarrow$0,
2$\rightarrow$1, and 7$\rightarrow$6 transitions
of CS.
The discrepancy between densities derived from C$^{18}$O and CS
can be resolved if the clumps have internal density
structure. Either smooth density gradients in clumps with sizes
just
below our angular resolution or a continuation of high-contrast
clumping to still smaller scales could account for the difference.
While we cannot rule out either of these pictures, it is noteworthy
that the scale of the C$^{18}$O observations (about 0.15 pc) is the
largest
for which the density discrepancy can be resolved with
smooth density gradients in unresolved clumps.}
% Here you write which journal accepted your paper, for example:
{accepted by The Astrophysical Journal}
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Previously unresolved IRAS sources in the $\rho$ Oph A cloud}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ D. Ward-Thompson }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{ Royal Observatory,
Blackford Hill,
Edinburgh, EH9 3HJ,
United Kingdom}
%% Within the following brackets you place your text:
{A maximum entropy method (MEM) is used to construct an IRAS image of the
central region of the $\rho$ Oph A dark cloud at each of the IRAS
wavebands (12, 25, 60 \& 100 $\mu$m), in which no prior information of
structure in the field is given to the maximum entropy routines. 6 sources are
detected at two or more wavebands in the 10$\times$12 arcmin area mapped. All 6
are coincident with near-IR sources known from ground-based observations,
however 4 of the 6 have not been previously separated in the IRAS data
using any other method. The other 2 sources, which are listed in the IRAS
Point Source Catalogue, were recovered by MEM in their correct positions. No
spurious, or unidentified sources were generated by MEM. Two other claimed
faint IRAS sources within the field, which are not however in the IRAS
Point Source Catalogue, were not detected by MEM. The typical gain in
resolution of the images reconstructed by MEM over standard methods is 1.5 - 2
in the in-scan direction, and 3 - 10 in the cross-scan direction. The mean FWHM
of the sources is 0.5 arcmin at 12 \& 25 $\mu$m, 1 arcmin at 60 $\mu$m and 1.5
arcmin at 100 $\mu$m. The flux densities and luminosities of all 6 sources are
derived, and the flux densities for the 2 known IRAS sources agree within
errors with those listed in the Point Source Catalogue. The flux
densities of 2 others are consistent with extrapolations of measurements made
at other wavelengths, and typical errors are estimated to be $\sim$ 10 - 30\%.
3-$\sigma$ upper limits are placed on the IRAS flux densities of the
sub-mm sources SM1 and VLA1623, which are lower than any previously obtained.
The 6 sources are classified according to their infra-red SED's.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Mon. Not. R. astr. Soc.}
\newpage
\begin{center}
{\Large\em New Books}
\end{center}
\vspace*{0.6cm}
{\Large\bf{Dust in the Galactic Environment}}
{\large\bf{D.C.B. Whittet}}
\vspace*{0.5cm}
{\bf 1. Introduction}
{\small{Dust in the Galaxy - our view from within;~~ Interstellar
environments; ~~The significance of dust; ~~The problem of grain composition}}
{\bf 2. Element abundances and depletions}
{\small{The origin and evolution of the chemical elements; ~~The Solar
System abundances - a standard reference; ~~ Abundance trends in the Galaxy;
~~The observed depletions }}
{\bf 3. Interstellar extinction and scattering}
{\small{Theory and methods;~~Average properties;~~Spatial variations in the
extinction curve;~~Models for interstellar extinction}}
{\bf 4. Interstellar polarization and grain alignment}
{\small{Extinction by non-spherical particles;~~Visual polarimetry of
reddened stars;~~The spectral dependence of polarization;~~Grain
alignment}}
{\bf 5. Spectral absorption features}
{\small{The 2175 \AA~feature;~~The optical diffuse bands;~~The infrared
absorption features}}
{\bf 6. Continuum and line emission}
{\small{Theoretical considerations;~~Continuum emission from the galactic
disk;~~Spectral emission features}}
{\bf 7. The origin and evolution of interstellar grains}
{\small{Dust in the ejecta of evolved stars;~~The evolution of dust in the
interstellar medium;~~Dust in the environments of young stars}}
{\bf 8. Towards a unified model for interstellar dust}
\vspace*{0.5cm}
IOP Publishing, Bristol, Philadelphia and New York
The Graduate Series in Astronomy
290 pages
\vspace*{0.5cm}
ISBN 0 7503 0204 6 hardcover 47.50 pounds or 95.00 dollars \\
ISBN 0 7503 0209 7 paperback 19.50 pounds or 39.00 dollars
Postage:
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\vspace*{0.5cm}
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\end{document}